The invention relates to improvements in molding apparatus in general, and more particularly to improvements in apparatus for converting thermoplastic blanks (e.g., tubular parisons) into shaped articles (e.g., into bottles or other blow molded articles).
Conventional apparatus for converting a series of thermoplastic blanks (e.g., blanks which consist of synthetic thermoplastic material) into shaped articles normally comprise a source of blanks, a heating unit which raises the temperature of successive blanks or successive groups of blanks to a desired temperature, one or more open-and-shut molds wherein the conversion of properly heated blanks into shaped articles takes place, and a transporting system which serves to advance blanks from the source to the heating unit, from the heating unit to the mold or molds and, if necessary, from the mold or molds to an article accepting station.
It is further known to provide a molding apparatus with a rotary conveyor which carries one or more molds. This creates problems because the mold or molds on the rotating conveyor must be connected with an energy source in order to ensure adequate heating of mold sections. In addition, and if the conversion of blanks involves blow molding of tubular or otherwise shaped hollow parisons into hollow shaped articles, the apparatus must further comprise means for supplying a pressurized gaseous fluid to the mold or molds on the rotary conveyor. All this contributes to complexity and higher initial and maintenance cost of the molding apparatus. Another drawback of such molding apparatus is that the transmission of signals from a stationary control unit to the movable and/or other components of the apparatus on the rotary conveyor also contributes to complexity of the apparatus and renders the apparatus more prone to malfunction with resulting prolonged periods of idleness. Removal of shaped articles from the molds on the rotary conveyor also contributes to the cost of the apparatus and prevents an increase of output above a rather modest value. Additional limits to the output are imposed by the means for transmitting energy and signals to the components on the rotary conveyor.